1. Technical Field
The present invention relates generally to a self-pressure tire regulator and, more specifically, to a mechanism incorporating solely on mechanical parts.
2. Discussion of Related Art
Air diffusion reduces tire pressure over time. The natural state of tires is under-inflated and maybe even over-inflated due to wrongfully maintenance. Accordingly, drivers must repeatedly act to maintain tire pressure or they will cause higher fuel consumption per kilometer, tire life reduction, vehicle handling lower performance and vehicle braking lower performance. Tire Pressure Monitoring Systems (TPMS) have been proposed to warn drivers when tire pressure is significantly low or high. Such systems, however, remain dependent upon the driver taking corrective action when warned to re-inflate a tire to recommended pressure.
Air temperature in a tire has a major effect on the pressure of air in the tire that must be considered in any approach to tire pressure maintenance. Ambient temperature variations and tire heating from rolling make tire temperatures and pressures denoting the amount of air in the tire. The pressure in a tire increases and decreases about 1 PSI with temperature increases and decreases of about 6° C. Normally, as a vehicle is driven the temperature in the tire increases due to the heat caused by friction from road contact and flexing of the side-walls causing a 2 to 5 PSI above its “cold” pressure (at ambient temperature). In addition, in practice tires are usually filled less often and while warm from driving. An ambient temperature drop of about 30° C., possible within a day and common within a month, reduces tire pressure by about 5 PSI. Thus, tire pressures frequently fall 8 PSI below the manufactures' requirement, typically 25%, without considering the normal leak rate of about 1 PSI per month.
Prior art presents a vast variety of self-inflating tire devices. The industry has attempted to solve the problem by offering electrical, electro-mechanical or mechanical devices, which work in association with such as U.S. Pat. No. 5,846,354, titled “tire pressure maintenance system”, where a gas transfer system is described that includes; power source, a pressure sensor, a control unit, and a gas transfer mechanism. Another example to this approach may be found in U.S. Pat. No. 5,558,730, titled “vehicle wheel including self-inflating tire pump”, where a pump is located inside the tire inflation region, provides a fixed tire pressure, comprised of many mechanical elements and requires a dedicated rim design.
It is desirable, therefore, to incorporate an automatic self-pressure regulator feature within the tire or as an add-on that will self-inflate the tire in order to compensate for any reduction in the tire pressure over time without a need for driver intervention. The automatic self-pressure regulator feature must also be small, simple, practical and inexpensive and that provides long term reliable operation (i.e. is fail safe such that failures do not cause deflation or over-inflation of a tire).